DE102010026986B4 - Knock Sensor System - Google Patents

Abstract

A knock sensor system comprising: a knock sensor for detecting vibration due to knocking of an internal combustion engine; first analog-digital converting means for analog-digital converting an output signal of the knock sensor at intervals of a predetermined time during a crank angle period during which vibration due to knocking occurs; second analog-digital converting means for analog-digital converting the output signal of the knock sensor at intervals of a predetermined time during a crank angle period during which mechanical noise occurs steadily; and knock sensor malfunction decision means for calculating the difference between an amplitude level of data converted by the second analog-to-digital conversion means and an amplitude level of data converted by the first analog-to-digital conversion means, wherein when the difference is below a malfunction decision level continuously over a plurality of piston strokes fall, it is decided that the knock sensor is malfunctioning.

Description

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a knock sensor system which detects a knock caused by an internal combustion engine. More particularly, the present invention relates to a knock sensor system having a malfunctioning device.

2. State of the art

A method for detecting a knocking phenomenon caused by a motor and using a vibration sensor (hereinafter, a knocking sensor) directly attached to a block of the engine is conventionally known. When knocking occurs during operation of the engine, it is known that vibration or vibration occurs in a natural frequency band, though it depends on the vibration mode of the engine or the knocking. The intensity of natural frequency vibration is measured to detect the knock.

Incidentally, when a malfunction occurs in a knock sensor for detecting the knocking, the knocking is not normally detected. It is therefore necessary to detect the malfunction in the knock sensor (malfunction detection). As a method, a method has been proposed for using a bias voltage for the knock sensor and monitoring the bias voltage to decide whether a malfunction occurs, such as a separation of the path to the knock sensor (for example, in Patent Document 1: JP-4-331329 ), or a method for detecting the vibration level of the knock sensor to decide whether the output characteristic of the knock sensor is different (for example, in Patent Documents 1, 2 and 3: JP H04-331 329 A . JP 3 302 219 B2 and JP 2 562 960 B2 ).

In Patent Document 1, it is described that the method of using a bias voltage may detect an on-state or an off-state, such as a knock sensor break or a short circuit, but a decrease in an output level due to wear of a piezoelectric Elements can not be captured very accurately. In Patent Document 1, there is disclosed a method in which, when a vibration level related to a rotation speed of a motor is equal to or smaller than a predetermined value, a decision is made that there is a malfunction. The method aims to detect the reduction in the output level due to wear of the piezoelectric element.

In Patent Document 2, it is disclosed that when a decision is made based on a vibration level, since a vibration level in a range of slow revolutions is smaller than the noise level to be folded when the knock sensor line is disconnected, a decision on a malfunction will not be made correctly can, unless a motor in a range slightly higher rotational speed (for example, 3000 rpm or more) is brought. In Patent Document 2, there is proposed a method which takes into consideration the fact that the vibration level of an engine greatly changes from one piston stroke to another. According to the method, a malfunction is detected based on the difference between the maximum value and the minimum value of the vibration levels detected over a predetermined number of piston strokes, so that it can be decided whether the knock sensor is malfunctioning even in a range of relatively low speeds (for example, 2000 rpm).

As long as an engine is brought into a revolution range in which the difference between the maximum value and the minimum value of the vibration levels detected over a predetermined number of piston strokes in a normal-working engine is greater than the difference between the maximum value and the minimum value of electrical noise level which are folded when the knock sensor line is disconnected and which are detected over the predetermined number of piston strokes, or the maximum value and minimum value of the engine vibration level detected during the predetermined number of piston strokes, if a sensor characteristic has wear, it can be decided correctly, whether the knock sensor has a malfunction. However, the vibration level of the engine is very low during a very small revolution speed, such as at idle (for example, 1000 rpm or less). The difference between the maximum and minimum values of the vibration levels detected during the predetermined number of piston strokes is small. Even if the method described in Patent Document 2 is used, it is difficult to decide whether the knock sensor is normal or abnormal. When a vehicle is not driven at a certain rotational speed (for example, 2000 rpm or more), it can not be decided whether the knock sensor is malfunctioning.

Moreover, in Patent Document 3, it is described that a knocking gate is set to a period of one piston stroke in which Oscillation level increases since a knocking has occurred, and a sensor malfunction noise gate is set to a period in which the oscillation level is high since no knocking has occurred, and a noise gate is set to a period in which a normal vibration occurs regardless of the presence or absence of knocking. The knock gate and noise gate are used to detect the knock, and the sensor malfunction noise gate is used to decide if the knock sensor is malfunctioning. However, since the vibration level detected in the sensor malfunction noise gate in a range of low rotational speeds is less than the noise level to be folded when the knock sensor line is disconnected, it is difficult even during this process to malfunction the knock sensor very low rotational speeds, such as during idling.

Out JP 2009-144 681 A is a Knockferfassungssystem known which can detect errors even at low speeds. In a phase in which no knocking is to be expected and mechanical noise occurs, the signal of a knock sensor is detected and evaluated. The peak value of the noise level is compared with a comparison value and detected if the value falls below the decision value.

SUMMARY OF THE INVENTION

The present invention solves the above problems. It is an object of the present invention to provide a knock detection system that can detect malfunction even at very low rotational speeds, such as at idle.

A knock sensor system according to the present invention includes: a knock sensor for detecting a vibration due to knocking of an internal combustion engine; a first analog-to-digital converting means for analog-to-digital converting an output signal of the knock sensor at intervals of a predetermined time during a crank angle period during which a vibration occurs due to knocking; a second analog-to-digital converting means for analog-to-digital converting the output signal of the knock sensor at intervals of a predetermined time during a crank angle period during which a mechanical noise continuously occurs; and a knock sensor error function decision means for calculating the difference between an amplitude level of data converted by the second analog-to-digital converting means and an amplitude level of data converted by the first analog-to-digital converting means, wherein if the difference is below a malfunction decision level continuously a plurality of piston strokes falls, it is decided that the knock sensor is malfunctioning.

According to the knock sensor system of the present invention, a malfunction decision is made on the basis of the difference of a vibration level observed during the period during which a vibration occurs due to a noise and a vibration level that occurs during the period during the one Vibration due to knocking occurs. When the knock sensor is disconnected, the deviation is small. When the knock sensor is operating normally, the difference increases, even at a very low rotational speed, such as at idle. Therefore, the malfunction of the knock sensor can be detected even during very low rotational speeds.

A knock sensor system according to the present invention includes: a knock sensor for detecting a vibration due to knocking of an internal combustion engine; a first analog-to-digital converting means for analog-to-digital converting an output signal of the knock sensor at intervals of a predetermined time during a crank angle period during which a vibration occurs due to knocking; a second analog-to-digital converting means for analog-to-digital converting the output signal of the knock sensor at intervals of a predetermined time during a crank angle period during which a mechanical noise continuously occurs; and a knock sensor error function decision means for storing a first amplitude level, which is an amplitude level of analog-to-digital converted data by the first analog-to-digital converting means, and a second amplitude level, which is an amplitude level of the second analog Digital Conversion Device Analog-to-digital converted data is obtained in connection with each piston stroke over a plurality of piston strokes and for calculating the deviation between the maximum of the second amplitude levels obtained in the plurality of piston strokes and the minimum of the first amplitude levels in the plurality of piston strokes, and if the deviation is continuously several times below a malfunction decision level, for deciding that the knock sensor is malfunctioning.

According to the knock sensor system of the present invention, the knock sensor failure determination means is provided for storing the first amplitude level, which is an amplitude level is detected during the period in which a vibration occurs due to knocking, and the second amplitude level, which is an amplitude level detected during the period in which a vibration due to a noise occurs in association with each Piston stroke across a plurality of piston strokes, and for storing the difference between the maximum of the second amplitude levels detected across the plurality of piston strokes and the minimum of the first amplitude levels detected across the plurality of piston strokes, and if the difference is continuously more Times below the malfunction decision level to decide that the knock sensor is malfunctioning. Therefore, when the knock sensor is operating normally, the difference continues to increase even during a very low rotational speed, such as at idle. Thus, the accuracy in detecting a malfunction of the knock sensor can be improved even in the range of very small rotational speeds.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

1 Fig. 13 is a construction diagram schematically showing an engine having a knock sensor system according to the present invention and a motor control unit;

2 Fig. 10 is a block diagram schematically showing the engine having the knock sensor system of the present invention and a motor control unit;

3 FIG. 10 is a block diagram showing a general configuration for knock control used in a knock sensor system according to Embodiment 1 of the present invention; FIG.

4A to 4C FIG. 12 is diagrams schematically illustrating a obtained vibration level when the knock sensor system is normal or malfunctioning; FIG.

5 FIG. 10 is a flowchart for describing malfunction detection performed in the knock sensor system according to Embodiment 1; FIG.

6A and 6B Fig. 10 is a diagram schematically showing a difference between the values Max_ns and Max_knk obtained when the knock sensor system is normal or malfunctioning;

7A and 7B Fig. 10 are diagrams schematically showing a deviation or variance when the knock sensor system is normal or malfunctioning;

8th FIG. 10 is a flowchart for describing a part of the malfunction detection performed in a knock sensor system according to Embodiment 2; FIG.

9 FIG. 10 is a flowchart for describing a part of the malfunction detection performed in the knock sensor system according to Embodiment 2; FIG.

10A and 10B Fig. 12 is diagrams schematically showing the occurrence of a noise derived from driving an injector and an embodiment 3;

11A and 11B Fig. 15 is diagrams schematically showing the occurrence of a noise derived from driving an intake valve and an embodiment 4;

12 FIG. 10 is a flowchart showing a part of malfunction detection performed in a knock sensor system according to Embodiment 5; FIG. and

13 FIG. 10 is a flowchart showing a part of malfunction detection performed in a knock sensor system according to Embodiment 7. FIG.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1

The embodiments of the present invention will be described below with reference to the drawings. 1 FIG. 13 is a construction diagram schematically showing an engine having a knock sensor system according to the present invention and a motor control unit. FIG. 2 FIG. 12 is a block diagram schematically showing the engine having the knock sensor system of the present invention and a motor control unit. FIG.

In 1 is an electronically controlled throttle valve 2 , which is electronically controlled to adjust an air intake flow rate, to an air intake system of the engine 1 upstream. To the degree of opening of the electronically controlled throttle valve 2 becomes a throttle aperture sensor 3 provided. A mechanical throttle valve, not shown and directly connected to a wire with an accelerator pedal, may be the electronically controlled throttle valve 2 replace. In addition, an air flow sensor 4 for measuring the air intake flow rate to the electronically controlled throttle valve 2 upstream. On the side of the engine 1 above the electronically controlled throttle valve 2 becomes a suction pipe pressure sensor 6 for measuring the pressure within a surge tank 5 arranged. Regarding the air flow sensor 4 and the intake manifold sensor 6 , either or both can be considered.

A variable intake valve unit 7 , adapted to vary or control the timing for opening or closing a suction valve, is attached to the suction valve located at a suction port above the surge tank 5 located. An injection valve 8th for injecting fuel is at the intake port. A variable moving exhaust valve unit 31 adapted to vary or control the timing for opening or closing an exhaust valve is connected to the exhaust valve disposed in an exhaust port. The injection valve 8th Can be arranged to feed fuel directly into a cylinder of the engine 1 inject. In addition, an ignition coil 9 and a spark plug 10 for use in igniting a mixed gas in the cylinder of the engine 1 , a crank angle sensor 11 for detecting a boundary of a disc fixed to a crankshaft to detect the rotational speed of the engine or a crank angle, and a knock sensor 12 arranged for detecting the vibrations of the engine.

In 2 become one through the airflow sensor 7 measured air inlet flow rate, through the intake manifold sensor 6 measured intake manifold pressure passing through the throttle aperture sensor 3 measured aperture of the electronically controlled throttle valve 2 , a pulse that is synchronous with the boundary of the disc connected to the crankshaft and that of the crank angle sensor 11 is output, and one of the knock sensor 12 measured waveform of the vibration of the motor 1 into the electronic control unit (hereinafter referred to as ECU or electronic control unit) 13 entered. In addition, measured values from various other sensors are input to the ECU. Further, signals are input which are sent from other control units (for example, an automatic transmission control system, brake control, and drive control).

The ECU 13 calculates a target throttle aperture based on the state of the accelerator pedal or the operating state of the engine and controls the electronically controlled throttle valve 2 , Based on the operating state, the variable-displacement intake valve unit 7 for varying or controlling the timing for opening or closing the intake valve and the injection valve 8th is controlled to achieve a given air-fuel ratio. Current flows to the ignition coil to achieve ignition at a given ignition timing. When a knock is detected by a later-described system, the predetermined ignition timing is set to a delayed timing to control or suppress the occurrence of knocking. Further, values are also calculated which are instructed to other different actuators.

Next, referring to 3 a knock control described in the ECU 13 is implemented. 3 FIG. 10 is a block diagram for showing a general configuration of the knock control in a knock sensor system in accordance with Embodiment 1 of the present invention. FIG. In 13 denotes reference numeral 12 and 13 a knock sensor or an ECU, as in 1 and 2 shown. The configuration of a knock control block in the ECU 13 is described below. The ECU 13 includes various interface circuits and a microcomputer. The microcomputer includes an analog-to-digital converter for converting an analog signal into a digital signal, a ROM area for storing control programs and control constants, and a RAM area for storing variables used to run a program allow.

reference numeral 14 denotes a knock control interface circuit, that is, a low pass filter (LPF) for removing high frequency components of a signal output of the knock sensor. reference numeral 15 denotes an analog-to-digital converter of the microcomputer. The analog-to-digital conversion implemented by the analog-to-digital converter is performed at intervals of a predetermined time (for example, 10 μs or 20 μs are provided). The LPF 14 includes an amplifier conversion unit that biases a vibration to 2.5V (setting the center of the vibration component to 2.5V) to all the vibration components in the analog-to-digital converter 15 to take into account. When the vibration components are low, the vibration components are amplified at 2.5V as the center voltage, so that the vibration components are restricted to the range of 0V to 5V with 2.5V as the center voltage. If the Vibration components are large, the vibration components are reduced to 2.5 V as the central voltage.

The analog-to-digital conversion can be performed at all times, and only data obtained during a period during which a knock occurs (for example, from a top dead center (TDC) to a crank angle of 50 After Top Death Center (ATDC) (abbreviated as A50) (hereinafter referred to as a knock detection period) may be applied to a Discrete Fourier Transform (DFT) processing circuit 16 and subsequent circuits are sent. (In the drawing, the period during which data is sent to the processing circuit 16 and subsequent circuits are transmitted, shown with an analog-to-digital window.) The knock detection period will be described below with reference to FIG 4A to 4C described. During a knock detection period during which knocking does not occur, as in FIG 4A As shown, the vibration components in a knock sensor signal are low and a different vibration resulting from knocking does not occur. During a period during which knocking occurs, as in 4B As shown, the vibration components occurring in the knock sensor signal are large, and a different vibration resulting from knocking occurs. Thus, the period during which the magnitude of the vibration components varies depending on the presence or absence of knocking is called the knocking detection period.

In the subsequent circuits 16a and 16b a time-frequency analysis is performed by digital signal processing. For digital signal processing, processing called discrete Fourier transform (DFT) or short-time Fourier transform (STFT) is performed to calculate a spectral current of various natural frequency components of the knock. For digital signal processing, an infinite impulse response (IIR) filter or a finite impulse response (FIR) filter may be used to sample the natural frequency components of the knock.

In the circuits 17a and 17b becomes a peak holding value of the in the circuits 16a and 16b calculated spectral current. The reference numerals 18a and 18b mean averaging circuits. The averaging circuits 18a and 18b use an equation given below to perform filtering to average the peak hold values calculated via respective piston strokes. VBGLa, b (n) = K1 × VBGLa, b (n-1) + (1-K1) × VPa, b (n) (1) where VBGL (n) denotes a filtered value, VP (n) denotes a peak hold value, K1 denotes averaging coefficient, and n denotes the number of piston strokes.

In the subsequent circuits 19a and 19b A threshold is obtained according to a following equation for use in deciding whether a knock has occurred. VTHa, b (n) = VBGLa, b (n) × Ktha, b + Vofs a, b (2) where VTH (n) denotes a threshold value, Kth denotes a threshold coefficient, and Vofs denotes a threshold offset value.

reference numeral 20a and 20b denote comparison calculation circuits. The comparison calculation circuits 20a and 20b compare the peak hold values with the threshold, decide whether knocking has occurred according to a following equation, and output a signal that is proportional to the intensity of knocking. VKa, b (n) = max {VPa, b (n) - VTHa, b (n), 0} (3) where VK (n) denotes a knock intensity (when VK (n) is greater than 0, a decision is made that there is knock).

reference numeral 21a and 21b designate ignition-to-ignition delay value calculation circuits. The ignition-to-ignition delay value calculating circuits 21a and 21b calculate a deceleration value that depends on a knock intensity detected at each ignition, according to an equation given below, on the basis of the results of the knock decision generated by the comparison calculation circuits 20a and 20b is carried out. ΔΘRa, b (n) = VKa, b (n) / VTHa, b (n) × Kg a, b (4) where ΔΘR denotes an ignition-to-ignition delay value and Kg denotes a delay value reflection value.

reference numeral 22 denotes a knocking delay value calculating circuit. The knocking delay calculating circuit 22 Integrates the larger of the through the calculation circuits 21a and 21b obtained ignition-to-ignition delay values and calculates a knock compensation value for an ignition timing. If no knocking occurs, the ignition timing becomes preset or reset. The calculation is calculated according to an equation given below. ΘR (n) = ΘR (n - 1) + max {ΔΘRa (n), ΔΘRb (n)} - Ka (5) where ΔΘR (n) denotes the knock compensation value and Ka is a preset reset constant.

The knock compensation value ΔΘ thus calculated is used to calculate a final knocking time according to an equation given below. ΘIG = ΘB - ΘR (n) (6) where ΘIG denotes the final ignition timing and ΘB denotes a basic ignition timing.

The processing method for implementing knock detection using the result of frequency analysis by digital signal processing by the circuits 16 to 22 and the implementation of a knock control for controlling a knock by delaying an ignition timing has been described so far.

Next, a malfunction decision processing method described by the present invention will be described below 3 shown circuits 23 to 25 performed in the knock sensor system. In one by the circuit 23 In the case of the knock detection period maximum amplitude calculation processing, the difference between the maximum and minimum values of the analog-to-digital converted values obtained during the knock detection period is regarded as the maximum amplitude obtained during the knock detection period. In one by the circuit 24 In accordance with the noise detection period maximum amplitude calculation processing, the difference between the maximum and minimum values of the analog-to-digital converted values obtained during the noise detection period is regarded as the maximum amplitude obtained during the noise detection period. For a method of detecting the analog-to-digital converted value during the noise detection period, as already mentioned, the analog-to-digital conversion device 15 which performs an analog-to-digital conversion at intervals of a predetermined time (for example, provided at 10 μs or 20 μs), perform an A / D conversion at any time and only data to the circuit 24 which is obtained during the period in which a mechanical noise occurs (for example, a period from a crank angle of 80 ° ATDC to a crank angle of 120 ° ATDC) (hereinafter referred to as a noise detection period). Alternatively, the A / D conversion may be performed alone during the noise detection period and the data obtained may be applied to this circuit 24 be transmitted.

A determination method for the noise detection period will be described below with reference to FIG 4A to 4C described. Whether noise does not occur during the noise detection period, as in 4A shown, or a noise occurs, as in 4B As shown, the vibration components are large and vibration occurs due to a steadily generated noise. The period during which the magnitude of the vibration components does not change depending on whether knocking has occurred and noiseless noise is constantly occurring is determined as the noise detection period.

Next, a malfunction decision process for the knock sensor system described by the circuit will be described below 25 is carried out. As long as the knock sensor system is operating normally, if no knocking occurs, as in 4A shown, or a knocking occurs, as in 4B 4, the vibration components during the noise detection period are large, and vibration arises due to a steadily generated noise. However, during the knocking detection period, a large vibration only occurs when knocking occurs. However, if no knocking occurs, the vibration components are very small. Moreover, as described above, when knocking occurs, an ignition timing is corrected to be late. Therefore, the knock does not occur steadily. The normal operating condition of the engine may be regarded as a condition in which knocking does not occur. Assuming that the difference between the maximum amplitude Max_ns obtained in the noise detection period and the maximum amplitude Max_knk obtained during the knock detection period is calculated, the difference takes a reasonably large value except at the time when a knocking occurs, as in 6A shown.

When a malfunction occurs in the knock sensor system, such as a disconnection, a short to a power source, or an electrical connection to ground, a vibration wave is as in FIG 4C shown with respect to a case where the knock sensor has failed to a certain extent folded regardless of the knock detection period or the noise detection period. The Vibration wave is not a vibration detected by the knock sensor, but is likely to be an electrical noise resulting from the wiring leading to the knock sensor, or a noise resulting from grounding or a change in the battery voltage.

The noise has an amplitude. Normally, the amplitude is larger than the amplitude that is obtained when a vibration level is low, such as during idling, and has little difference between the knocking detection period and the noise detection period. Assuming that the difference between the maximum amplitude Max_ns obtained during the noise detection period and the maximum amplitude Max_knk obtained during the knock detection period is calculated as in a normal state, the difference decreases as shown in FIG 6B shown at all times a relatively small value. The difference is significantly different when the knock sensor is normal and when the knock sensor malfunctions. Therefore, as long as a malfunction criterion is set to an appropriate value, it can be decided whether the knock sensor is normal or malfunctioning. Even if the output characteristic of the knock sensor is greatly weakened due to the wear of a piezoelectric element, the difference between the maximum amplitude Max_ns obtained during the noise detection period and the maximum amplitude Max_knk obtained during the knock detection period becomes smaller. Therefore, an abnormality in the characteristic of the sensor can be detected.

5 describes the malfunction detection processing used by the knock sensor system by the in 3 shown circuits 23 to 25 be performed. Regarding 5 In the following, the malfunction detection processing for the knock sensor system will be described. The malfunction detection processing for the in 5 Knock sensor system shown is performed at a time after the analog-to-digital conversion, which is performed while the knock detection period and noise detection period over a current piston stroke is completed, and before an analog-to-digital conversion performed during the knock detection period or noise detection period over a subsequent piston stroke has begun. Specifically, the malfunction detection processing is performed at interrupted processing timings in synchronization with the revolution of the engine, such as at a crank angle of 5 ° BTDC (a time that does not overlap with the knock detection period nor with the knock detection period) or with interrupted processing times that have occurred. when the A / D conversion is performed during the later from the knock detection period and the noise detection period. First, in step S101, the maximum amplitude Max_knk which is obtained during the knocking detection period is calculated. The maximum amplitude can, as already mentioned, be calculated as the difference between the maximum and minimum values obtained during the knock detection period. Thereafter, in step S102, the maximum amplitude Max_knk which is obtained during the noise detection period is calculated. The maximum amplitude Max_knk can, as already mentioned, be calculated as the difference between the maximum and minimum values obtained during the noise detection period. In step S103, it is decided whether the difference between the maximum amplitude Max_ns obtained during the noise detection period and the maximum period Max_knk obtained during the knock detection period is smaller than the criterion.

When the difference between the maximum amplitude Max_ns obtained during the noise detection period and the maximum amplitude Max_knk obtained during the knock detection period is smaller than the criterion, a decision is made that the knock sensor is malfunctioning. In step S104, a normal state counter is reset to an initial value (for example, the fifth piston stroke). In step S105, a value of a malfunction counter is decreased. When the difference between the maximum amplitude Max_ns obtained during the noise detection period and the maximum amplitude Max_knk obtained during the knock detection period is equal to or greater than the criterion, a decision is made that the knock sensor system is operating normally. In step S106, the malfunction counter is reset to an initial value (for example, 100 piston strokes). In step S107, the value of the normal state counter is decreased.

In step S108, it is decided whether the malfunction counter indicates 0. If the malfunction counter indicates 0, it is assumed that a malfunction decision has continued for a predetermined number of piston strokes (multiple piston strokes). A malfunction flag is set at step S110. If the malfunction decision counter does not indicate 0, it is decided in step S109 whether the normal function counter indicates 0. If the normal function counter indicates 0, it is assumed that a normal function decision has continued for a predetermined number of piston strokes (multiple piston strokes). The malfunction decision flag is cleared in step S111. If a decision is made in step S109 that the normal function counter does not indicate 0, nothing is done (the malfunction decision flag remains intact) and the process is terminated.

In 5 the difference between the maximum amplitude Max_ns obtained during the noise detection period and the maximum amplitude Max_knk obtained during the knock detection period is compared with the criterion. Alternatively, the difference between an amplitude value obtained during the noise detection period (besides the maximum amplitude, for example, an average of amplitude values or an integral value thereof) and an amplitude value obtained during the knock detection period (in addition to the maximum amplitude) may be obtained Example, an average of amplitude values or an integral value thereof) are compared with the criterion to decide if a malfunction has occurred. When the malfunction decision for the knock sensor system is made as mentioned above, when the vibration amplitude value of the knock sensor is monitored, it can be decided very accurately whether the knock sensor system malfunctions even in a range of very low revolution speeds, such as during idling it was hard to make a decision in the past. Therefore, the malfunction decision for the knock sensor system can be satisfactorily performed in all ranges of engine revolution speeds. When a deviation continuously exceeds a malfunction decision level over a plurality of piston strokes, a knock sensor failure determination device decides that the knock sensor is normal. Even if the knock sensor is reset from a malfunctioning state to a normal state, a decision that the knocking sensor is operating normally can be made quickly.

Embodiment 2

Next, an embodiment 2 will be described below. Embodiment 2 has a difference from Embodiment 1. This difference is described below. With respect to Embodiment 1, it has been described that the decision as to whether a knock sensor operates normally is based on the fact that when knocking does not occur, as in FIG 4A The difference in vibration amplitudes between the knock detection period and the noise detection period is shown to be large. More specifically, in steps S101 to S103, the 5 the difference of the maximum amplitudes between the knock detection period and the noise detection period within the same piston stroke is compared with the criterion to decide whether the knock sensor is malfunctioning.

However, depending on the individual variability of a motor or a motor rotation speed, the difference in the amplitude of the vibration components between the knock detection period and the noise detection period may be large (A in FIG 7A ) or small (B in 7A ), as in 7A with respect to a case in which knocking does not occur. When the difference in the amplitudes of a vibration component is subject to variance, there is a fear that a deterioration in accuracy in the error function decision may occur to the knock sensor. In the embodiment 2, the difference between the minimum of the maximum amplitudes obtained during the knocking detection periods within a predetermined number of piston strokes equal to or greater than 2 and the maximum of the maximum amplitudes obtained during the noise detection periods is calculated, and the malfunction decision for the knock sensor is made based on the difference. Even in this case, when the knock sensor malfunctions, the difference between the noise detection period and the knock detection period is small, as in FIG 7B shown.

In order to implement Embodiment 2, steps S101 and S102 in FIG 5 with respect to embodiment 1 as in FIG 8th and 9 shown modified. In steps S401 to S403 in FIG 8th is, equivalent to step S101 in 5 which calculates minimum Max_knk of the maximum amplitudes obtained during the knock detection period within the predetermined number of piston strokes equal to or greater than 2. In step S401, the stored values of the maximum amplitudes obtained during the knocking detection period within respective piston strokes at the end of the immediately preceding piston stroke are shifted. In step S402, the maximum amplitude obtained during the knock detection period during a current piston stroke is calculated. The calculation method is identical to that which is performed in step S101 in FIG 5 is used. Namely, the difference between the maximum value and the minimum value obtained during the knocking detection period is calculated. In step S403, the minimum Max_knk of the maximum amplitudes obtained during the respective knock detection periods within the predetermined number of piston strokes are calculated according to an equation given below. Max_knk = min {Max_knk (n), Max_knk (n - 1), Max_knk (n - (k - 1)) wherein Max_knk (n) denotes the maximum amplitude obtained during the knock detection period within the nth piston stroke, where n denotes the present piston stroke and k denotes the predetermined number of piston strokes equal to or greater than 2.

At the time the engine starts or starts, all Max_knk (n) values are set to the initial value of zero. In this case, only the value obtained during the first piston stroke after starting is identical to the value of Embodiment 1. The advantage of embodiment 2 is given by the values obtained during the second and subsequent piston strokes. In steps S501 to S503 in FIG 9 is, equivalent to step S102 in 5 , the maximum Max_ns of the maximum amplitudes obtained during the noise detection periods within the predetermined number of piston strokes equal to or greater than 2 are calculated. In step S501, the stored values of the maximum amplitudes obtained during the noise detection periods within the piston strokes at the end of the immediately preceding piston stroke are shifted. In step S502, the maximum amplitude obtained during the noise detection period within the present piston stroke is calculated. The calculation method is identical to that which is performed in step S102 in FIG 5 is used. Namely, the difference between the maximum value and the minimum value obtained during the noise detection period is calculated. In step S503, the maximum Max_ns of the maximum amplitudes obtained during the noise detection periods within the predetermined number of piston strokes is calculated according to the following equation. Max_ns = min {Max_ns (n), Max_ns (n-1), ..., Max_ns (n - (k-1))} where Max_ns (n) denotes the maximum amplitude obtained during the noise detection period within the nth piston stroke, where n denotes the current piston stroke and k denotes the predetermined number of piston strokes equal to or greater than 2.

At the time of starting the engine, if all Max_ns (n) values are set to an initial value of zero, only the value obtained within the first piston stroke after starting the engine is identical to the value in the embodiment. The advantage of embodiment 2 results from the values obtained within the second and the subsequent piston strokes. After the sub-processes are finished, the process after step S103 in FIG 5 executed. More specifically, in step S103 in FIG 5 It is decided whether the difference between the maximum Max_ns of the maximum amplitudes obtained during the noise detection periods within the predetermined number of piston strokes equal to or greater than 2 and the minimum Max_knk of the maximum amplitudes obtained during the knock detection periods is smaller than the criterion is. Based on the result of the decision, the process goes to step S104 or S106 in FIG 5 continued. The subsequent steps are identical to those of Embodiment 1.

In step S103 in FIG 5 the difference between the maximum Max_ns of the calculated maximum amplitudes obtained during the noise detection periods within the predetermined number of piston strokes equal to or greater than 2 and the minimum Max_knk of the maximum amplitudes obtained during the knock detection periods is compared with the criterion. Alternatively, the difference between the maximum of the calculated amplitude values (besides the maximum amplitudes, for example, average amplitude values or integral values thereof) obtained during the noise detection periods within the predetermined number of piston strokes equal to or greater than 2 and the minimum of the amplitude values ( in addition to the maximum amplitudes, for example, average amplitude values or integral values thereof) obtained during the knock-detecting periods are compared with the criterion to decide whether a malfunction has occurred.

Due to the fact that whether the knock sensor is malfunctioning as described above, even if the difference in the amplitudes of the vibration component between the noise detection period and the knock detection period is subject to fluctuation, by monitoring the vibration level of the knock sensor in a range very low rotational speeds, such as idle, it is decided whether the knock sensor is malfunctioning.

Embodiment 3

Next, Embodiment 3 will be described below. As compared with Embodiments 1 and 2, Embodiment 3 is characterized in that noise specified by driving an intra-cylinder direct injection type injector as a mechanical noise. A basic implementing means is identical to that in Embodiments 1 and 2. In the following, only one difference will be described. This in 1 shown injection valve is arranged to inject a fuel directly into the cylinder of the engine 1 inject. The noise detection period was in connection with 4 and is defined with fixed values, such as a crank angle of 80 ° ATDC and a crank angle of 120 ° ATDC. Since the noise resulting from the driving of the injector is determined, the noise detection period in Embodiment 3 varies as in FIGS 10A and 10B shown in synchronism with the start time of the injection valve control.

Regarding 10A and 10B the case of a four-cylinder engine is described. When the start timing of the injection valve driving, as in 10A is set to a crank angle of 260 ° before top dead center (BTDC), for varying or controlling the injection valve drive timing, by a variable controller, the mechanical noise occurs in the vicinity of a crank angle of 100 ° ATDC on.

Therefore, means is provided for setting the noise detection period to a crank angle period during which a second analog-to-digital converter performs an analog-to-digital conversion to a period of, for example, a crank angle of 80 ° ATDC to a crank angle of 120 ° ATDC according to the injector drive timing, which is controlled by the variable control means, so that the noise detection period can completely cover the timing of the crank angle in the vicinity of 100 °.

If, in 10B When the injector drive start timing is set to a crank angle of 220 ° BTDC, the mechanical noise due to the injection valve driving occurs in the vicinity of a crank angle of 140 °. Means is provided for setting a noise detection period to a crank angle period during which the second analog-to-digital converter performs an A / D conversion, for example, to a period from a crank angle of 120 ° ATDC to a crank angle of 160 ° ATDC according to the injection valve Driving timing, which is controlled by the variable control device, so that the noise detection period can completely cover the times of the crank angle in the vicinity of 140 ° ATDC. Therefore, the embodiment 3 is characterized in that the noise detection period can be varied depending on the injector drive timing.

As described above, noise resulting from the driving of the injector is specified as a mechanical noise. Further, the noise detection period is provided according to injector drive timing. Thereby, the mechanical noise can be detected more accurately, and whether there is a malfunction in the knock sensor is decided on the basis of the mechanical noise. Finally, whether the knock sensor is malfunctioning can be decided by monitoring the knock sensor vibration level, even in a range of very low rotational speeds, such as idle.

Embodiment 4

Next, Embodiment 4 will be described below. In comparison with Embodiments 1 and 2, Embodiment 4 is characterized in that noise resulting from driving to open and close the intake valve or the exhaust valve is specified as mechanical noise. A basic implementation is identical to Embodiment 1 or 2. Only the difference will be described below. The noise detection period was in connection with 4 is described as being defined with the fixed values of a crank angle of, for example, 80 ° ATDC to a crank angle of 120 ° ATDC. Since the noise resulting from the driving for opening and closing the intake valve or the exhaust valve is specified, the noise detection period in Embodiment 4 as in FIGS 11A and 11B shown varies in synchronism with the opening or closing timing of the intake valve or exhaust valve.

Regarding 11A and 11B the case will be described in which a noise resulting from driving to close an intake valve of a four-cylinder engine is assumed. In particular, when the intake valve closing timing, as in FIG 11A is set to a timing of a crank angle of 70 ° after the bottom dead center and the bottom dead center (ABDC), respectively, by a controllably movable intake valve mechanism 7 that varies or controls the intake valve closing timing, the mechanical noise due to the close control of the intake valve in the vicinity of the crank angle of 70 ° ABDC. Therefore, means is provided for determining the noise detection period as a crank angle period during which the second analog-to-digital converter performs an analog-to-digital conversion to a period of, for example, the crank angle from 70 ° ATDC to a crank angle of 120 ° according to intake valve timing. Closing time, by the controllable inlet valve mechanism 7 is controlled, so that the noise detection period the time of the crank angle in the vicinity of 70 ° ATDC completely can cover. In Embodiment 3, the timing of the occurrence of the mechanical noise is considered to be in the vicinity of the noise detection period. This is because the noise resulting from the driving of the injector is observed by the knock sensor in the vicinity of the drive timing, while the noise resulting from the opening or closing control of the intake valve or exhaust valve is often at a crank angle of approximately 20 ° to 30 ° thereafter is observed because of the adverse effect of the patency of a cam disk.

When the intake valve closing timing, as in 11B shown, to a crank angle of 50 ° ABDC is set by the controllable intake valve mechanism 7 that varies or controls the closing timing of the intake valve, the mechanical noise due to the intake valve closing control occurs in the vicinity of a crank angle of 50 ° ATDC. Therefore, means is provided for setting a crank angle period as a noise detection period during which the second analog-to-digital converter performs an analog-to-digital conversion to a period of, for example, a crank angle of 50 ° ATDC to a crank angle of 100 ° ATDC , according to the intake valve closing timing provided by the controllably movable intake valve mechanism 7 is controlled so that the noise detection period can completely cover the timing of the crank angle in the vicinity of 50 ° ATDC. When the knock detection period and the noise detection period succeed each other, as in FIG 11B or overlap, the analog-to-digital conversion with respect to the knock detection period and the analog-to-digital conversion with respect to the noise detection period are better performed together. After the analog-to-digital conversion is completed, data units may be distributed to the knock detection period and the noise detection period.

A description was made in the case of the intake valve closing timing. Even if the controllable intake valve mechanism 7 varies or controls the intake valve opening timing, the same process mentioned above can be followed. Further, even if a controllably movable exhaust valve mechanism is used to vary or control the exhaust valve opening / closing timing, as long as means for determining a crank angle period may be provided, while the second analog-to-digital converter is an analog-to-digital converter. Performing conversion, according to the opening or closing timing of the exhaust valve controlled by the controllably movable exhaust valve mechanism, the same process mentioned above is followed. Therefore, Embodiment 4 is characterized in that the noise detection period is determined according to the opening or closing timing of the intake valve or the exhaust valve.

As mentioned above, the noise resulting from driving to open or close the intake valve or exhaust valve is specified as a mechanical noise. Further, the noise detection period is determined according to the opening or closing timing of the intake valve or the exhaust valve. Accordingly, the mechanical noise is more accurately detected, and it is judged whether the knock sensor is malfunctioning based on the detected mechanical noise. Even in a range of very low rotational speeds, such as idling, it can be decided by monitoring the vibration level of the knock sensor whether the knock sensor is malfunctioning.

Embodiment 5

Next, Embodiment 5 of the present invention will be described below. The embodiment 5 is characterized in that the embodiments employed in the embodiments 3 and 4 are switched according to the operating state of the engine. Although noise resulting from driving the injection unit has a certain strength regardless of the engine revolution number, noise resulting from the opening and closing control of the intake valve or exhaust valve has a tendency to increase along with an increase in engine revolution number. Therefore, an engine revolution number at which the noise resulting from the driving of the intake valve or exhaust valve becomes larger than the noise resulting from the driving of the injection unit is stored in advance as a set value. When an engine revolution number is smaller than the set value, the noise resulting from the driving of the injection unit is selected to switch the methods employed in Embodiments 3 and 4. When the engine revolution speed is greater than the set value, the noise is selected, which is the drive for opening or closing the intake valve or exhaust valve to switch the methods. Thus, it can be satisfactorily decided in all ranges of engine revolutions whether the knock sensor is malfunctioning.

Embodiment 5 will be described with reference to FIG 12 described. First, in step S201, a current engine revolution speed is calculated. The current rotational speed may be calculated based on a limit distance associated with a predetermined crank angle, which is indicated by the in 1 shown crank angle sensor 11 is detected. In step S202, it is decided whether the engine rotation speed ne is smaller than the set value. At the set value, an engine revolution speed (for example, 2000 r / min) is set at which the noise resulting from driving to open or close the intake valve or exhaust valve is greater than the noise resulting from the driving of the injection unit, such as previously described.

If it is decided that the engine rotation speed ne is smaller than the set value, the process proceeds to step S203. Similar to Embodiment 3, means is provided for determining the crank angle period (noise detection period) during which the second analog-to-digital converter performs analog-to-digital conversion according to injection unit drive timing. If it is decided that the engine rotation speed is equal to or greater than the set value, the process proceeds to step S204. Similar to Embodiment 4, means is provided for determining the crank angle period (noise detection period) during which the second analog-to-digital conversion device performs analog-to-digital conversion according to the opening or closing timing of the intake valve. If the engine revolution speed is less than the set value, the noise resulting from the driving of the injection unit is appropriately selected to exchange the processes. When the engine revolution speed is greater than the set value, the noise resulting from the intake valve opening or closing control is selected to exchange the procedures.

Incidentally, a case has been described in which noise from driving results in opening or closing of the intake valve. Even in a case where the noise from the drive results in the opening or closing of the exhaust valve, the noise detection period is determined in step S204 according to the opening or closing timing of the exhaust valve. After the above procedure is completed, the malfunction detection method for the in conjunction with 5 performed in connection with embodiment 1 or 2 knock sensor described. Thus, it can be satisfactorily decided in all areas of the engine rotation speed whether there is a malfunction in the knock sensor. It can be accurately detected even if the degree that the cause of a noise adversely affects, depending on the engine revolution speed, whether the knock sensor is malfunctioning.

Embodiment 6

Next, an embodiment 6 will be described below. Embodiment 6 is characterized in that Embodiment 1 is applied to an operation range in which an engine rotation speed is low. In the prior art, in an operating range of high engine revolution speeds, since it can be decided whether the knock sensor is malfunctioning, the embodiment is specifically applied to an operation range in which the engine revolution number is small. In the high engine revolution speed range, for example, a related art is known in the art, which decides when a vibration level associated with a certain engine revolution speed is equal to or less than a predetermined value, malfunction has occurred, and described in Patent Document 1 is and is used to decide if the knock sensor is malfunctioning.

Specifically, a revolution speed at which a vibration level in a normal state is higher than the vibration level of a noise, which is folded in a case where a connection to the knock sensor is disconnected, is stored in advance as a set value. When an engine rotation speed is less than the set value, Embodiment 1 is selected. If the engine revolution speed is greater than the set value, the related method is selected. Thus, it can be satisfactorily decided in all ranges of engine revolution speeds whether the knock sensor is malfunctioning. The method described in Patent Document 1 is taken as an example of the prior art. Alternatively, any other method can be used. Thus, while deciding whether a malfunction has occurred using a well-established technology in the range of high rotational speeds, it can be decided in the low rotational speed range whether a malfunction has occurred in which the prior art can not be used to decide to meet. Therefore, in all ranges of engine revolution speeds, it can be satisfactorily decided whether the knock sensor is malfunctioning. Moreover, even if the extent to which the cause of a noise adversely varies depending on the engine revolution speed, whether the knock sensor has a malfunction can be accurately detected.

Embodiment 7

Next, an embodiment 7 will be described below. Embodiment 7 is characterized in that Embodiments 2 and 3 are applied to an operation range in which an engine revolution speed is low. In the prior art, in a range of high engine revolution speeds, since it is judged whether the knock sensor is malfunctioning, Embodiments 2 and 3 are used in an operation range in which the engine revolution speed is low. In the area where the engine revolution speed is high, it is judged whether the knock sensor is malfunctioning using the prior art. In particular, a noise resulting from the driving of the injection unit has a certain strength regardless of the engine revolution speed. When the engine rotation speed is low, the noise level is higher than a noise level attained during the knock detection period in which knocking does not occur. As the engine revolution speed becomes higher, there is a tendency for a higher noise level due to engine vibration.

An engine revolution speed at which the noise due to the vibrations of the engine itself becomes larger than the noise resulting from the driving of the injection unit is stored in advance as a setting value. When an engine revolution speed is less than the set value, a malfunction is detected due to the difference between the maximum of the noise resulting from the driving of the injection unit and measured equal to or greater than 2 during the noise detection periods within a predetermined number of piston strokes, and the minimum of the noise measured during the knock-detection periods. When the engine rotation speed is greater than the set value, the knock detection period is regarded as a noise detection period, and a malfunction is detected based on the difference between the maximum of the noise measured during the knock detection periods within the predetermined number of piston strokes equal to or greater than 2, and the minimum of it. Thus, it can be satisfactorily decided in all ranges of engine revolution speeds whether the knock sensor is malfunctioning. If the engine revolution speed is greater than the set value, and if the knock detection period is regarded as the noise detection period, then the present process is identical to the process described in Patent Document 2. However, if the engine revolution speed is greater than the set value, it can be decided using the prior art whether the knock sensor is malfunctioning. Although the method described in Patent Document 2 has been used as an example, any other method may be used.

Embodiment 7 will be described below with reference to FIG 13 described. First, in step S301, a current engine revolution speed ne is calculated. The current engine speed of rotation may be calculated based on a limit distance associated with a predetermined crank angle, which is defined by the in-line speed 1 shown crank angle sensor 11 is detected. In step S302, it is decided whether the engine rotation speed ne is smaller than the set value. As a set value, an engine revolution speed (for example, 2000 r / min) at which the vibration level of a noise due to the vibrations of the engine itself is determined higher than the vibration level of a noise resulting from the driving of the injection unit is determined as described above. If a decision is made that the engine rotation speed ne is smaller than the set value, the process proceeds to step S303. Similar to Embodiment 3, the noise detection period is set to a crank angle period that depends on the injector drive timing. When a decision is made that the engine rotation speed ne is equal to or greater than the set value, the process proceeds to step S304 and the knock detection period is determined as the noise detection period. Thereafter, a malfunction detection processing is performed for the knock sensor described in connection with Embodiment 2 with reference to FIG 5 has been described. Thus, if the engine revolution speed is less than the set value, a malfunction decision is made for the knock sensor based on the noise resulting from the driving of the injector. If the engine revolution speed is greater than the set value, a malfunction decision is made for the knock sensor based on vibration noise of the engine itself (for example, the method described in Patent Document 2 or any other related method may be used). Thus, it can be satisfactorily decided in all ranges of engine revolution speeds whether the knock sensor is malfunctioning.

Claims (9)

Knock sensor system, with: a knock sensor for detecting a vibration due to knocking of an internal combustion engine; a first analog-to-digital converting means for analog-to-digital converting an output signal of the knock sensor at intervals of a predetermined time during a crank angle period during which a vibration occurs due to knocking; a second analog-to-digital converting means for analog-to-digital converting the output signal of the knock sensor at intervals of a predetermined time during a crank angle period during which a mechanical noise continuously occurs; and a knock sensor error function decision means for calculating the difference between an amplitude level of data converted by the second analog-to-digital converting means and an amplitude level of data converted by the first analog-to-digital converting means, wherein when the difference is continuously below a malfunction decision level a plurality of piston strokes falls, it is decided that the knock sensor is malfunctioning. The knock sensor system of claim 1, wherein the knock sensor failure function decision means obtains a maximum amplitude as an amplitude level of analog-to-digital converted data by the second analog-to-digital converting means, a maximum amplitude as an amplitude level of the analog-to-digital conversion means. Obtains digital-converted data, calculates the difference between the maximum amplitude of the A / D converted by the second A / D converter and the maximum amplitude of the A / D converted by the first A / D converter, and If the difference continuously drops below a malfunction decision level over a plurality of piston strokes, it judges that the knock sensor is malfunctioning. Knock sensor system, with: a knock sensor for detecting a vibration due to knocking of an internal combustion engine; a first analog-to-digital converting means for analog-to-digital converting an output signal of the knock sensor at intervals of a predetermined time during a crank angle period during which a vibration occurs due to the knocking; a second analog-to-digital converting means for analog-to-digital converting the output signal of the knock sensor at intervals of a predetermined time during a crank angle period during which a mechanical noise continuously occurs; and Knock sensor fault function decision means for storing a first amplitude level, which is an amplitude level of analog-to-digital converted data by the first analog-to-digital converting means, and a second amplitude level, which is an amplitude level of the second analogue level. Digital Conversion Device Analog-to-digital converted data, in conjunction with each piston stroke over a plurality of piston strokes, and calculating the deviation between the maximum of the second amplitude levels obtained in the plurality of piston strokes and the minimum of the first amplitude levels obtained in the plurality of piston strokes, and, if the deviation is continuously several times below a malfunction decision level, for deciding that the knock sensor is malfunctioning. The knock sensor system of claim 3, wherein the knock sensor malfunction decision means obtains a first maximum amplitude as a first amplitude level of analog-to-digital converted data by the first analog-to-digital converter, a second maximum amplitude as a second amplitude level of the second analog Digital Conversion Device Receives Analog-to-Digital Converted Data Storing First Maximum Amplitude and Second Maximum Amplitude Associated with Each Piston Stroke Through a Variety of Piston Strokes, The Deviation Calculates Between the Maximum of the Second Maximum Amplitudes Obtained in the Variety of Piston Strokes and the minimum of the first maximum amplitudes obtained in the plurality of piston strokes, and when the deviation continuously drops several times below the malfunction decision level, decides that the knock sensor is malfunctioning. A knock sensor system according to any one of claims 1 to 4, wherein, when the deviation continuously exceeds the malfunction decision level over the plurality of piston strokes or continuously several times, the knock sensor failure determining means decides that the knock sensor is normal. A knock sensor system according to any one of claims 1 to 4, wherein the malfunction decision by the malfunction decision means is performed in an operation range in which an engine revolution speed is less than a set value. A knock sensor system according to any one of claims 1 to 4, further comprising: variable control means for varying or controlling an injector drive timing; and means for determining a crank angle period during which the second analog-to-digital converting means performs analog-to-digital conversion according to the one of the variable Control device controlled injection valve drive timing. A knock sensor system according to any one of claims 1 to 4, further comprising: a controllably movable valve mechanism for varying or controlling the opening or closing timing of an intake valve or exhaust valve; and means for determining a crank angle period during which the second analog-to-digital converter performs analog-to-digital conversion according to the opening or closing timing of the intake valve or exhaust valve controlled by the controllably movable valve mechanism. A knock sensor system according to any one of claims 1 to 4, further comprising: variable control means for varying or controlling an injector drive timing and a variably movable valve mechanism for varying or controlling the opening or closing timing of an intake valve or exhaust valve; and means for determining, in an operating range in which an engine revolution speed is less than a set value, the crank angle period during which the second analog-to-digital converter performs an A / D conversion according to the injector drive timing controlled by the variable control device; and determining, in an operating range in which the engine revolution speed is greater than the set value, the crank angle period during which the second analog-to-digital converter performs an analog-to-digital conversion according to the opening or closing timing of the valve movable by the variable valve mechanism Intake valve or exhaust valve.

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